1. Field of the Invention
The invention relates to a pressure wave machine with integrated combustion and a method for cooling the rotor of this pressure wave machine.
2. Discussion of Background
Compared with turbines which have a steady-state type of operation, the known pressure wave machines, which have a non-steady-state type of operation, have the great advantage that they permit very high hot gas temperatures. This applies particularly to pressure wave machines with integrated constant volume combustion, such as are described--with the associated methods--in U.S. Pat. No. 4,719,746 and U.S. Pat. No. 5,197,276 for example.
Because the cells are periodically subjected to cool air and hot combustion gas, the rotor assumes a material temperature which is substantially less than the hot gas temperature. Nevertheless, problems of excessive rotor temperatures can arise, under certain conditions, even with pressure wave machines. This is so where very high specific powers are demanded and, therefore, very high gas temperatures are necessary or where the pressure wave machine is not equipped with a symmetrical counterflow pressure wave process but is equipped with a wave process which leads to an asymmetrical temperature distribution in the axial direction within the rotor.
The latter is, for example, the case in the parallel flow process in which the outlet end of the rotor is subjected substantially more intensively to hot gas than the inlet end. Because this parallel flow process is advantageous with respect to the design integration of the pressure wave machine in a gas turbine, however, a way must be found of cooling the rotor. The known use of cooling air compressors or an external cooling medium for rotor cooling does, however, involve a relatively large amount of complication for a small effect.